The present invention relates to a double spindle grinding machine able to grind two works of the same shape simultaneously by a single grinding machine.
The interiors of the nozzle parts in a diesel engine, for example, have tapered front ends and cylindrical portions. To grind each internal portion precisely, two processes of grinding are required. In the conventional grinding machine, however, only one grinding spindle is provided for each workpiece in most cases, so that only one work can be grinded during one working process of a grinding machine even by speeding up the working process of the grinding machine. In the case where plural working processes are required to be performed on one work, it is impossible to yield double or triple productivity by each grinding machine since the grinding speed of each grinding machine is limited.
On the contrary, the multi-spindle grinding machine has recently been developed, in which plural work spindles located opposite respectively to plural grinding spindles are held by a drum, and each work is grinded simultaneously to perform one working process, and the drum is incrementally rotated unidirectionally via a Geneva device or the like intermittently after each one working process is finished. The multi-spindle grinding machine has the advantage of speeding up the working in comparison with the conventional type since plural working processes are carried out by one grinding machine.
However, the multi-spindle grinding machine has various drawbacks as follows.
(1) Since the drum which holds the plural work spindles intermittently rotates unidirectionally, it is necessary to move a stopper of a positioning device during the course of each increment of rotation to be in contact with or spaced from the drum. As a result, the positioning device is complicated and the accuracy of positioning is deteriorated.
(2) As the drum rotates unidirectionally, the piping and wiring of the lubricating system towards each work spindle and the automatic chucking device of the works are complicated.
(3) Since the driving motors of each of the work spindles are mounted on the drum, the movement of the drum slows down by the weight of the motors.
(4) It is necessary to provide the driving motors corresponding to the respective work spindles to make a difference in the grinding conditions.
The present invention aims to eliminate the above noted conventional drawbacks of the multi-spindle grinding machine, and therefore it is an object of the present invention to provide a double spindle grinding machine able to work two workpieces simultaneously in two processes at a high speed and high precision. The double spindle grinding machine is realized by reversing at least a pair of work spindles symmetrically provided on a supporting frame fixed on a swing shaft at 180.degree. after one working process is finished and positioning the pair of work spindles again opposite to respective grind stones, whereby a stopper of a positioning device is fixed, and the piping and wiring mechanism of the lubricating system is simplified. The motors for driving the work spindles are separately provided by transmitting the rotation of the work spindles to a center of rotation of the swing shaft by way of a coaxial intermediate shaft.